The present invention relates to devices for lifting relatively large and heavy structures. The invention relates more particularly to a lifting device for lifting an aircraft engine so that the engine can be attached to engine mounting structure on an aircraft.
During installation of an aircraft engine on an aircraft wing, the engine must be lifted up to the wing for mounting the engine on a strut attached to the wing. Where the aircraft wing has dihedral, the engine generally must be rotated about its axis to properly align it with the dowel pins that project downwardly from the strut and that are received into holes in the engine mounts on the engine for supporting shear loads between the engine and the strut. Then, the aircraft engine can be secured to the wing with appropriately sized threaded fasteners that support the tension loads between the engine and the strut.
This installation process is complex, requires close coordination between operators, and can present potential hazards to the loading equipment, the aircraft, the engine, and the operators. Aircraft engines are extremely heavy and present high loading factors during installation. For example, engines for jumbo aircraft, such as the Boeing 777 series aircraft, can weigh in excess of 20,000 pounds. Further, the wings of jumbo aircraft, such as the Boeing 777 series aircraft, can be a considerable height above the ground. Thus, mounting an engine on a jumbo aircraft, such as a Boeing 777 series aircraft, entails lifting an aircraft engine weighing up to 20,000 pounds or more to a strut that can be up to 15 feet off the ground.
Because of the size and weight of aircraft engines for jumbo aircraft, the aircraft engine should be handled as little as possible in order to minimize the likelihood of equipment damage or injuries to personnel. However, installing an aircraft engine using known techniques requires removing the aircraft engine from the aircraft engine""s shipping cradle. These known techniques include the use of overhead bridge cranes with slings, a xe2x80x9cbootstrapxe2x80x9d system that is temporarily mounted on the aircraft wing, and known loaders such as those described in U.S. Pat. Nos. 4,440,265 and 4,461,455. The extra step of transferring the aircraft engine from its shipping cradle necessitated by the use of these known loading methods requires extra tooling and makes these known methods time consuming and expensive. It would be desirable to provide an engine loader that could obviate the necessity of removing the engine from its shipping cradle prior to lifting it to the aircraft.
Further, known loaders such as those described above can only be used to lift the particular aircraft engine they are designed to lift, and cannot accommodate any other aircraft engines. Thus, loading multiple types of aircraft engines with known loaders requires multiple types of loaders. This significantly increases the costs of procuring and maintaining the loading equipment.
Thus, there is an unmet need in the art for an aircraft engine loader that can be used to lift an aircraft engine that is still in the aircraft engine""s shipping cradle or to lift a cradle and dolly for an engine, and for an aircraft engine loader that can be used to load multiple types of aircraft engines.
The present invention addresses the above needs by providing an engine uplift loader that can lift an aircraft engine while still in its shipping cradle for mounting the engine to engine mounting structure on an aircraft. Further, the loader in accordance with a preferred embodiment of the invention can be used for loading different types of engines.
According to one aspect of the invention, an engine uplift loader includes a frame assembly having generally parallel first and second frame members spaced apart by a distance enabling the shipping cradle and engine to be positioned between the first and second frame members. A plurality of lifting devices are supported on the frame assembly extending upwardly therefrom, each lifting device being operable to raise and lower an upper end of the lifting device relative to the frame assembly along a generally vertical lifting axis. An attachment assembly is mounted to the upper end of each lifting device, each attachment assembly being structured and arranged to attach to the shipping cradle such that raising the upper ends of the lifting devices causes the shipping cradle and engine to be lifted upwardly. At least one of the attachment assemblies is movably mounted on the respective lifting device such that the attachment assembly can be selectively positioned in various positions relative to the lifting axis of the lifting device so as to accommodate different configurations of shipping cradles. Thus, the engine can be lifted while still in its shipping cradle, and the engine uplift loader can accommodate more than one configuration of engine and cradle.
Preferably, the lifting devices include attachment fittings mounted adjacent to the upper ends of the lifting devices, and the attachment assemblies include cable assemblies that are removably attached to the attachment fittings. The cable assemblies removably attach the aircraft engine shipping cradle to the loader and are arranged to permit attachment to shipping cradles of different types of aircraft engines. A load monitoring device can be attached to each cable assembly for monitoring the load exerted on the engine and shipping cradle by the engine uplift loader.
The attachment fittings that are movably mounted on their lifting devices preferably are mounted by a slide assembly structured and arranged to permit the attachment assembly to be slid along a horizontal axis. Preferably, each of the first and second frame members supports two spaced-apart lifting devices, and the slide assembly is employed on only one of the two lifting devices for adjusting the distance between the attachment assemblies on the two lifting devices.
According to another aspect of the invention, the frame assembly includes a plurality of fluid cushion bearings that depend downwardly from the frame assembly. The fluid cushion bearings permit the loader to be supported on a fluid film so that it can be readily maneuvered to align the engine with the engine mounting structure on the aircraft.
The engine uplift loader can include a plurality of jacks attached to the frame assembly and operable to be extended in engagement with the supporting surface to urge the engine uplift loader upwardly to maintain a preload between the engine and the engine mounting structure on the aircraft. The loader can also include wheels for transporting the loader along the supporting surface.
In accordance with another aspect of the invention, the frame assembly of the loader comprises a generally U-shaped frame assembly having spaced, generally parallel first and second frame members each having a first end and a second end, and a third frame member extending between the first ends of the first and second frame members. The frame assembly defines an opening between the second ends of the first and second frame members through which the engine on the shipping cradle can be received such that the engine and shipping cradle are disposed between the first and second frame members. Each of the first and second frame members includes a pair of lifting devices spaced apart therealong. Where it is desired to be able to vary the distance between the attachment assemblies that attach to the shipping cradle so as to accommodate different types of engines and cradles, one of the lifting devices on each frame member can include a slide assembly or other type of movable mount for the attachment assembly, as previously described.
The lifting devices preferably comprise fluid-operated cylinders such as hydraulic cylinders, and the cylinders preferably incorporate relief valves for relieving fluid pressure in the cylinders should such pressure exceed a predetermined value. Accordingly, the engine uplift loader is self-relieving to prevent damage to the loader and/or to the aircraft as a result of abnormally large forces therebetween that could arise from various causes.